The Mossberg 590 was developed by O.F.Mossberg & Sons company (USA) in the mid-1970s as a "military specifications" (adopted for US Military) modification of the Mossberg model 500 shotgun. "Militarization" included strengthening of the receiver and other parts, installation of the vented heat-shield around the barrel, bayonet lug, and extended magazine, as well as an aluminum trigger guard instead of plastic one. Standard finish is Parkerizing, and the gun is usually provided with replacement pistol grip, which allows easy conversion to 'Cruiser' modification and back. Since 1987, this shotgun is a standard equipment of US Armed forces; while it was officially replaced in the US Army with Benelli M1014 semi-automatic shotgun, Mossberg 590 shotguns are still widely used by US Navy and US Marine Corps.